Fastener installation apparatus for installing self-attaching fasteners in mass production applications, such as automotive applications, typically include a fastener installation head which includes a reciprocating plunger for installing a self-attaching fastener in a panel opposite the plunger passage, and a die member or die button which supports the panel and deforms the panel into a recess provided in the fastener, permanently installing the fastener in the panel. There are several types of self-attaching fasteners, including pierce and clinch nuts as disclosed, for example, in U.S. Pat. No. 3,648,747, assigned to the assignee of the predecessor in interest of this application. The pierce nut disclosed in this patent includes a rectangular pilot which pierces an opening in the panel and flange portions on opposed sides of the pilot having panel bearing faces and dovetail-shaped or “re-entrant” grooves in the bearing surface of the flanges on opposed sides of the pilot. The pierce nuts may be interconnected by frangible connectors, such as wires, as shown, for example, in U.S. Pat. No. 3,845,860, also assigned to the predecessor in interest of the assignee of this application, or the self-attaching nuts may be delivered to the fastener installation head in bulk form.
The fastener installation apparatus of this invention may also be utilized to install T-shaped pierce nuts, as disclosed in U.S. Pat. No. 3,152,628, or clinch nuts as disclosed in U.S. Pat. No. 2,750,660. Both of these patents are also assigned to the predecessor in interest of this application. Although the fastener installation head of this invention is not specifically designed for installing cold-formed self-attaching fasteners, such as the installation head disclosed in U.S. Pat. No. 5,042,518, also assigned to the predecessor in interest of the assignee of this application, the principles of this invention may be also utilized for such applications.
As set forth above, the fastener installation apparatus of this invention is particularly, but not exclusively, for an application having limited or restricted space, wherein the plunger which drives the self-attaching fastener into the panel must have a very limited or short stroke as compared to conventional self-attaching fastener installation heads, sometimes referred to as “pressure pierce heads.” U.S. Pat. No. 4,505,416 assigned to the assignee of the predecessor in interest of this application discloses a pressure pierce head for such applications. As disclosed in this patent, the self-attaching fastener installation head includes a fixed member and a moveable member resiliently biased away from the fixed member by a coil spring and the fixed member includes a plunger which reciprocates through a plunger passage in the moveable member, such that a self-attaching fastener is installed in a panel located opposite the plunger passage with each stroke of a press. The fixed member may be installed in a conventional die press, which simultaneously forms the panel, or the pressure pierce head may be utilized in a separate press assembly as described further below. However, the pressure pierce installation head disclosed in U.S. Pat. No. 4,505,416 had several problems including wear of the guide shanks or bolts resulting in limited life in mass production applications and the moveable member, which includes a feed passage, is formed of a single block of metal requiring replacement of the entire moveable member in the event of damage to the moveable member. Also, the pressure pierce installation head disclosed in this patent is subject to alignment problems because the plunger was not sufficiently guided by the guide bolts for rugged use in mass production applications. Another problem was that it was not practical to include a sensor, such as a proximity probe, in this head design.
The pressure pierce head disclosed in U.S. Pat. No. 4,505,416 was then replaced by the pressure pierce head assembly disclosed in U.S. Pat. No. 6,442,830, assigned to the assignee of this application, the disclosure of which is incorporated by reference. The pressure pierce head disclosed in U.S. Pat. No. 6,442,830 has several important advantages over the pressure pierce head disclosed in U.S. Pat. No. 4,505,416, particularly including more accurate guidance of the guide shank by incorporating a bushing surrounding the guide shank and thus better guidance of the plunger, resulting in more rugged construction. Another advantage of the pressure pierce head disclosed in U.S. Pat. No. 6,442,830 is reduced maintenance costs. The moveable member is comprised of a face plate or nut track and a nut cap, which are bolted together, and the nut passage is defined between the face plate and the nut cap, permitting replacement of either of these components following damage or wear. The plunger passage is defined by aligned openings in the face plate and nut cap and a nose plate and the movement of the moveable member assembly is limited by keepers attached to the fixed member, rather than the guide bolts.
As will be understood by those skilled in this art, it is very important to assure that a fastener is received through the feed passage into the plunger passage prior to actuation of the fastener installation apparatus. U.S. Pat. No. 6,442,830 discloses a conventional proximity probe located in the plunger passage opposite the feed passage which indicates the presence or absence of a fastener in the plunger passage prior to actuation of the press. That is, a fastener received through the feed passage engages the head of the proximity probe, indicating the presence of a fastener in the plunger passage. The proximity probe is then connected to the control of the press in a conventional manner permitting actuation of the press when a fastener is located in the plunger passage. However, this conventional arrangement results in wear or damage to the proximity probe in mass production applications. Further, the leg of the plunger required a machined slot to clear the proximity probe during actuation, resulting in additional expense. It would thus be desirable to avoid direct contact of the fastener with the proximity probe.
Another problem associated with all conventional installation apparatus for self-attaching fasteners is installing self-attaching fasteners in close proximity in a panel. In a conventional self-attaching fastener installation head, the spacing of the fasteners in a panel is limited by the size of the nose or moveable member. That is, where two self-attaching fasteners are to be installed in a panel in relatively close relation, the spacing between the fasteners is limited by the combined width of the adjacent nose members of the installation heads and the installation heads must be spaced in the die assembly. In many applications, however, it would be desirable to attach self-attaching fasteners to a panel in relatively close proximity, wherein the spacing between the self-attaching fasteners is less than the combined width of the adjacent nose members of the separate installation heads. Further, as will be understood by those skilled in this art, the installation heads must be spaced in the die assembly to avoid interference between the installation heads and to provide adequate support for the installation heads.
The improved fastener installation apparatus of this invention solves these problems by avoiding contact of the fasteners with the proximity probe and permits the simultaneous installation of two or more self-attaching fasteners in a panel in relatively close proximity. As will be understood from the following description of the fastener installation apparatus of this invention, these improvements may be utilized in combination or separately.